Dehydration behavior of a natural hydrated Ca-chabazite studied by in-situ high-temperature single-crystal X-ray diffraction
Dehydration behavior of a natural hydrated Ca-chabazite studied by in-situ high-temperature single-crystal X-ray diffraction
复制标题
原位高温单晶X射线衍射研究天然水合钙菱沸石的脱水行为
DOI：
10.1016/j.micromeso.2020.110648
复制
发表时间：
2021
影响因子：
5.2
通讯作者：
K. Fujiwara
中科院分区：
文献类型：
--
作者：
A. Nakatsuka;N. Kawata;K. Fujiwara
本文用原位高温单晶X射线衍射数据研究了天然水化钙菱沸石（Ca_（1.57）Na_（0.49））（Al_（3.39）Si_（8.55））O_（24）·12.47）H_2 O在100、200和250 °C的脱水行为。在之前在室温（RT）结构中发现的五个水位点（OW 1-OW 5）和四个可交换阳离子位点（Ca 1-Ca 4）中，本结构分析揭示了在100 °C下存在OW 1、OW 4、Ca 3位点，在200和250 °C下存在OW 3、Ca 3、Ca 4位点。还揭示了新的框架外位点的存在：在100 °C的OW 2 '位点和在200和250 °C的Ca 5位点。从温度依赖性的占领这些骨架外网站，脱水和阳离子迁移过程总结和合理化如下。随着加热至100 °C，与可交换阳离子没有键的OW 3水分子完全解吸。同时，Ca 1和Ca 2阳离子失去了大量的水分子作为配体（OW 1和OW 5为Ca 1，OW 4为Ca 2）;这导致两种阳离子同时迁移到相邻的Ca 3位点，被更多的配体包围。随着进一步加热至250 °C，与可交换阳离子没有键的OW 2 '水分子完全解吸。同时，大多数Ca 3阳离子通过失去大量的水分子作为配体（OW 1，OW 4）而迁移到相邻的Ca 4和Ca 5位点。在100-250 °C的温度范围内解吸的一部分水分子迁移到OW 3位点以与剩余的Ca 3阳离子键合。骨架结构中Si/Al− O 1、−O2和−O3键长的特殊温度依赖性可以用它们的键价变化来解释，这是由于脱水和阳离子迁移过程造成的。另一方面，Si/Al− O 4键长的变化主要受热膨胀效应而不是键价效应的影响。
Dehydration behavior of a natural hydrated Ca-chabazite with composition (Ca1.57Na0.49)(Al3.39Si8.55)O24·12.47H2O has been studied by the structure analyses based on thein-situhigh-temperature single-crystal X-ray diffraction data at 100, 200 and 250 °C. Among the five water sites (OW1–OW5) and four exchangeable-cation sites (Ca1–Ca4) found previously in the room-temperature (RT) structure, the present structure analyses revealed the presence of OW1, OW4, Ca3 sites at 100 °C and of OW3, Ca3, Ca4 sites at 200 and 250 °C. The presence of the new extraframework sites was also revealed: OW2’ site at 100 °C and Ca5 site at 200 and 250 °C. From the temperature dependence of the occupation for these extraframework sites, the dehydration and cation migration processes are summarized and rationalized as follows. With heating up to 100 °C, OW3 water molecules, having no bonds to exchangeable cations, are completely desorbed. Simultaneously, Ca1 and Ca2 cations lose the large amounts of water molecules as ligands (OW1 and OW5 for Ca1, OW4 for Ca2); this brings about the simultaneous migration of both cations to adjacent Ca3 site, surrounded by more ligands. With further heating up to 250 °C, OW2’ water molecules, having no bonds to exchangeable cations, are completely desorbed. Simultaneously, most of the Ca3 cations migrate to adjacent Ca4 and Ca5 sites by losing the large amounts of water molecules as ligands (OW1, OW4). A part of the water molecules desorbed in the temperature range of 100–250 °C migrate to OW3 site to be bonded to the remaining Ca3 cations. The peculiar temperature dependence of Si/Al−O1, −O2 and −O3 bond lengths in the framework structure can be explained in terms of their bond-valence variations due to such dehydration and cation migration processes. On the other hand, the variation of Si/Al−O4 bond length is dominated by thermal expansion effect rather than the bond valence effect.
登录
查看更多内容
DOI：
10.1016/s0167-2991(02)80346-9
发表时间：
2002
期刊：
Studies in Surface Science and Catalysis
影响因子：
--
作者：
E. Passaglia;O. Ferro
通讯作者：
O. Ferro
影响因子：
5.2
作者：
A. Nakatsuka;Hironao Okada;K. Fujiwara;N. Nakayama;T. Mizota
通讯作者：
A. Nakatsuka;Hironao Okada;K. Fujiwara;N. Nakayama;T. Mizota
具有菱沸石骨架的沸石中阳离子和分子的位置。
影响因子：
5.4
作者：
J. Pluth;J. V. Smith;W. Mortier
通讯作者：
W. Mortier
天然菱沸石中的阳离子位点位置
DOI：
10.1107/s0567740882003483
发表时间：
1982
期刊：
Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry
影响因子：
--
作者：
M. Calligaris;G. Nardin;L. Randaccio;P. C. Chiaramonti
通讯作者：
P. C. Chiaramonti
DOI：
10.1016/s0144-2449(82)80075-4
发表时间：
1982-01-01
期刊：
ZEOLITES
影响因子：
--
作者：
ALBERTI, A;GALLI, E;ZANAZZI, PF
通讯作者：
ZANAZZI, PF